JP3684518B2 - Resist pattern formation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, in the lithographic techniques used in the manufacturing process of the semiconductor device, a method of forming a resist pattern using a valid resin coating materials to form a fine resist pattern.
[0002]
Needless to say, high integration of semiconductor devices is currently required, but in order to realize this, a technique for miniaturizing circuit patterns is required. High resolution and low reflection of the substrate are required.
[0003]
Here, for the shortening of the exposure wavelength, for example, DUV (deep ultraviolet) light is used, but the development field is limited, but for resists, development of chemically amplified resists containing photoacid generators is active. In order to reduce the reflection of the substrate, various types of BARC (bottom antireflective coating) materials are being developed. The present invention is a technique for forming a fine pattern using a chemically amplified resist. It can contribute to improvement.
[0004]
[Prior art]
In general, when a pattern is formed using a chemically amplified resist, for example, a spin coating method is applied to form a resist film, the resist film is subjected to a first heat treatment (prebake), and then subjected to ultraviolet rays or far ultraviolet rays. The pattern is exposed.
[0005]
In a chemically amplified resist, acid is usually generated only in the exposed portion, and in the case of a positive resist, the generated acid is a base material due to a second heat treatment (post exposure bake: PEB) after exposure. A pattern is formed when developed to solubilize the resin, and the acid generated during this process can solubilize many base resins as a catalyst, thus achieving high resist sensitivity. It is what is done.
[0006]
As long as it is described above, it seems that a fine pattern can be easily formed by using a chemically amplified resist, but various problems actually occur.
[0007]
In other words, since chemically amplified resists utilize acid catalysis, when the surface is contaminated with basic molecules such as ammonia and amines in the air when a film is formed, it occurs after exposure. Since the acid is deactivated by the basic molecule and the resist surface is insolubilized during development, pattern resolution failure and line width variation occur.
[0008]
The basic molecules in the air are not always at a constant concentration in the clean room, and therefore the pattern may change between lots.
[0009]
In order to avoid this, an acidic or neutral resin coating material that protects the resist surface from basic molecules in the air is applied.
[0010]
[Problems to be solved by the invention]
As described above, when a chemically amplified resist is simply used, the pattern formation is realized as designed due to the influence of basic molecules in the air, resulting in poor pattern resolution and fluctuations in line width. In some cases, the resist surface is protected by applying an acidic or neutral resin coating material.
[0011]
However, when the means for applying the resin coating material is employed, the contrast of the optical image is lowered due to focus shift in the exposure apparatus or focus shift due to a step in the wafer. It is difficult to maintain the resist in a good shape over a wide range of focus, and there is little margin of the resist shape with respect to defocusing in the exposure apparatus.
[0012]
Even if the resin coating material film is not used, such a decrease in the depth of focus occurs in the same manner if no basic molecule is present, and if the basic molecule is excessively present. In this case, since the resolution failure occurs, the same occurs.
[0013]
FIG. 10 is a cutaway side view of a main part showing a resist film in a process essential point for explaining a case where exposure is performed in a defocused state and a pattern is formed.
[0014]
FIG. 10A shows an exposed state, where 1 is an object to be etched, 2 is a chemically amplified resist film, 2A is an exposed portion, 2B is an unexposed portion, and 3 is a wavelength irradiated through a mask. DUV light of 248 [nm], 4 indicates a light intensity profile, and 5 indicates a protonic acid generated by irradiation with DUV light.
[0015]
As is apparent from the figure, in the defocused state, the proton acid 5 is generated on the surface of the unexposed portion 2B due to the wraparound of the DUV light due to the decrease in the contrast of the optical image.
[0016]
FIG. 10B shows a developed state, and 6 shows a resist pattern with a reduced film thickness.
[0017]
The protonic acid 5 shown in FIG. 10 (A) acts to remove the protecting group in the resist base resin after PEB, so that when the development is performed, the resist is easily dissolved in the developer. .
[0018]
As described above, since the protonic acid 5 is also generated on the surface of the unexposed portion 2B, dissolution of the resist occurs there, and as shown in FIG. Will be formed.
[0019]
According to the present invention, when a pattern is formed using a chemically amplified resist, a simple means is employed to obtain a pattern with little film loss and a rectangular cross section.
[0020]
[Means for Solving the Problems]
In the present invention, when a pattern is formed using a chemically amplified resist film, the surface of the resist film is kept very slightly basic before or during the exposure, and the acid generated in the exposed portion is slightly deactivated, so that the resist It is fundamental to realize a resist film having a pattern in which the solubilization is suppressed and, as a result, the film loss is small and the cross section is rectangular.
[0021]
FIG. 1 is a cutaway side view of the main part showing the structure in the vicinity of the resist film at the main points of the process for explaining the principle of the present invention. Do the same symbols as those used in FIG. 10 indicate the same parts? Or it shall have the same meaning. In this case, it is assumed that the exposure is performed in a defocused state.
[0022]
FIG. 1A shows an exposed state, 7 shows a resin coating material film according to the present invention, and this resin coating material film 7 has very little basicity.
[0023]
As is apparent from the figure, in the present invention, in the defocused state, the contrast of the optical image is lowered, and the surface of the unexposed portion 2B has the protonic acid 5 due to the wraparound of the DUV light. In terms of occurrence, it is exactly the same as the conventional technique.
[0024]
However, according to the present invention, the slight amount of protonic acid 5 generated on the surface of the chemically amplified resist film 2, particularly on the surface of the unexposed portion 2B, is due to the presence of the resin coating material film 7 having a slight basicity. Since it is deactivated, it does not contribute to the dissolution of the resist film 2.
[0025]
FIG. 1B shows a developed state, and 8 shows a resist pattern with little film reduction and a substantially rectangular cross-sectional shape.
[0026]
The resist pattern 8 having a good shape as shown in FIG. 1B is obtained because the protonic acid 5 generated on the surface of the unexposed portion 2B due to the wraparound of the DUV light is caused by the resin coating material film 7. Therefore, the surface of the unexposed portion 2B can be kept insoluble.
[0027]
From where it said, is at the Relais resist pattern forming method Yi to the present invention, the step of performing a first heat treatment step after forming a chemically amplified resist film on a substrate, then the chemically amplified resist film A step of forming a resin coating material film comprising a water-insoluble polyolefin-based polymer and an aromatic amine, aliphatic amine, or alkylamine-based basic compound; A step of performing a second heat treatment, and then a step of developing after peeling the resin coating material film.
[0029]
The resin coating material film used when the resist pattern is formed by carrying out the present invention satisfactorily prevents the penetration of basic molecules from the air. Of course, the resin coating material film originally contains a very small amount of basic molecules, and the basic molecules are the surface layer of the chemically amplified resist film. Therefore, even if an extra small amount of acid is generated on the surface of the unexposed portion of the resist pattern due to the wraparound of light generated due to the decrease in the contrast of the optical image at the time of defocusing, It is possible to inactivate the acid and insolubilize the chemically amplified resist film. Therefore, the film loss caused by the decrease in the contrast of the optical image at the time of defocusing etc. It can contribute to solving the problem.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
An example of an embodiment in the present invention will be described.
[0031]
(1) About 0.7 [μm] of KRF-K2G (trade name of JSR), which is a positive chemical amplification resist made by JSR (Japan Synthetic Rubber Co., Ltd.), on a wafer having a diameter of 15 [cm] (6 inches). Apply to a thickness of.
[0032]
(2) On the hot plate, heat treatment is performed at a temperature of 80 [° C.] and a time of 120 [seconds].
[0033]
(3) By applying the spin coating method, the resin coating material according to the present invention is applied to a thickness of about 0.2 [μm].
[0034]
(4) On the hot plate, heat treatment is performed at a temperature of 60 ° C. and a time of 90 seconds.
[0035]
(5) Excimer laser stepper with a wavelength of 248 [nm] (NSR-2005EX8A, manufactured by Nikon Corporation, NA = 0.5, σ = 0.5) is used to perform exposure while changing the focus.
[0036]
(6) On the hot plate, heat treatment is performed at a temperature of 100 [° C.] and a time of 120 [seconds].
[0037]
(7) Immerse in xylene (100 [%]) and peel off the resin coating material film according to the present invention.
[0038]
(8) Paddle development was carried out for 60 seconds using a developer composed of an aqueous solution containing 2.38% TMAH (tetramethyl ammonium hydroxide) as a main component.
[0039]
The resin coating material of the present invention used in the process described above is a polyolefin-based resin, di-cyclohexyl-amine (concentration of 1000 [ppm] in the range of 100 [ppm] to 10000 [ppm] with respect to the resin content). The solvent is xylene.
[0040]
Moreover, as a basic compound,
Aromatic amines (1) Di-cyclohexyl-amine (2) Aniline and its derivatives (3) Benzylamine and its derivatives
Aliphatic amines (1) Isopropylamine [0042]
Alkylamines and the like can be used.
[0043]
In the resist pattern formed as described above, the cross-sectional shape of 0.3 [μm] L / S (line and space) is 2.0 [μm] in the focus range (centering on half of the resist film thickness). In the range of ± 1.0 [μm]).
[0044]
Incidentally, in the conventional technique, that is, with a resist pattern formed using a resin coating material film having an amine concentration of 0, the same separation resolution of 0.3 [μm] L / S as described above is possible. It is only within a focus range of 4 [μm] (a range of ± 0.7 [μm] centering on half of the resist film thickness). According to the present invention, the focus margin is clearly improved. It was.
[0045]
FIG. 2 to FIG. 5 are main part slope views showing the resist film for explaining the relationship between the focus and the resist film cross-sectional shape when the present invention is implemented. Each figure was created by faithfully tracing micrographs.
[0046]
Various conditions related to the sample used when obtaining this data are as follows.
Base resin for chemically amplified resist: ZCOAT (trade name: manufactured by Nippon Zeon)
Dicyclohexylamine concentration (vs. resin): 1000 [ppm]
Pattern: 0.3 [μm] L / S
[0047]
In each figure, F indicates the focus position, and it can be seen that the best cross-sectional shape is obtained when F = −0.6 [μm] from the data listed. .
[0048]
In FIG.
(A) is for F = −1.6 [μm], (B) is for F = −1.4 [μm], and (C) is for F = −1.2 [μm].
[0049]
In FIG.
(A) is the case where F = −1.0 [μm], (B) is the case where F = −0.8 [μm], and (C) is the case where F = −0.6 [μm].
[0050]
In FIG.
(A) is the case where F = −0.4 [μm], (B) is the case where F = −0.2 [μm], and (C) is the case where F = 0.0 [μm].
[0051]
In FIG.
(A) is the case where F = 0.2 [μm], and (B) is the case where F = 0.4 [μm].
[0052]
6 to 9 are oblique views of the main part showing the resist film for explaining the relationship between the focus and the resist film cross-sectional shape when the conventional technique is implemented. Each figure was created by faithfully tracing micrographs.
[0053]
In FIG.
(A) is for F = −1.6 [μm], (B) is for F = −1.4 [μm], and (C) is for F = −1.2 [μm].
[0054]
In FIG.
(A) is the case where F = −1.0 [μm], (B) is the case where F = −0.8 [μm], and (C) is the case where F = −0.6 [μm].
[0055]
In FIG.
(A) is the case where F = −0.4 [μm], (B) is the case where F = −0.2 [μm], and (C) is the case where F = 0.0 [μm].
[0056]
FIG. 9 shows the case where F = 0.2 [μm].
[0057]
Various conditions relating to the sample used when obtaining this data were obtained when the data shown in FIGS. 2 to 5 were obtained, except that the dicyclohexylamine concentration (vs. resin) was 0 ppm. The conditions are exactly the same as the sample used.
[0058]
From the data listed, it can be seen that the focus range is clearly narrow and that the resulting cross-sectional shape is not as good as that according to the present invention.
[0059]
【The invention's effect】
Is In Relais resist pattern forming method Yi to the present invention, subjected to a first heat treatment step after forming a chemically amplified resist film on a substrate, then a water-insoluble polyolefin to the chemically amplified resist film on A resin coating material film containing a polymer and an aromatic amine, aliphatic amine, or alkylamine basic compound, and then subjected to a second heat treatment after pattern exposure, Development is performed after the resin coating material film is peeled off.
[0060]
The resin coating material film used when the resist pattern is formed by carrying out the present invention satisfactorily prevents the penetration of basic molecules from the air. Of course, the resin coating material film originally contains a very small amount of basic molecules, and the basic molecules are the surface layer of the chemically amplified resist film. Therefore, even if an extra small amount of acid is generated on the surface of the unexposed portion of the resist pattern due to the wraparound of light generated due to the decrease in the contrast of the optical image at the time of defocusing, It is possible to inactivate the acid and insolubilize the chemically amplified resist film. Therefore, the film loss caused by the decrease in the contrast of the optical image at the time of defocusing etc. It can contribute to solving the problem.
[Brief description of the drawings]
FIG. 1 is a cutaway side view of a main part showing a configuration in the vicinity of a resist film at a process point for explaining the principle of the present invention.
FIG. 2 is a main part perspective view showing a resist film for explaining a relationship between a focus and a resist film cross-sectional shape when the present invention is implemented;
FIG. 3 is a perspective view of a principal part showing a resist film for explaining a relationship between a focus and a resist film cross-sectional shape when the present invention is carried out.
FIG. 4 is a perspective view of a principal part showing a resist film for explaining the relationship between the focus and the cross-sectional shape of the resist film when the present invention is carried out.
FIG. 5 is a perspective view of a principal part showing a resist film for explaining the relationship between the focus and the cross-sectional shape of the resist film when the present invention is carried out.
FIG. 6 is a principal part perspective view showing a resist film for explaining a relationship between a focus and a resist film cross-sectional shape when a conventional technique is implemented.
FIG. 7 is a principal part perspective view showing a resist film for explaining a relationship between a focus and a resist film cross-sectional shape when a conventional technique is implemented.
FIG. 8 is a main part slope view showing a resist film for explaining a relationship between a focus and a resist film cross-sectional shape when a conventional technique is implemented.
FIG. 9 is a principal part perspective view showing a resist film for explaining a relationship between a focus and a resist film cross-sectional shape when a conventional technique is implemented.
FIG. 10 is a cross-sectional side view of a main part showing a resist film at a process essential point for explaining a case where a pattern is formed by performing exposure in a defocused state.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Etching object 2 Chemical amplification resist film 2A Exposed part 2B Unexposed part 3 DUV light irradiated through the mask, for example, 248 [nm] 4 Light intensity profile 5 Proton generated by irradiation with DUV light Resist pattern 7 with reduced acid 6 film Resin coating material film 8 according to the present invention Resist pattern with less film loss and substantially rectangular cross-sectional shape

Claims (1)

Forming a chemically amplified resist film on the substrate and then applying a first heat treatment step;
Next, forming a resin coating material film containing a water-insoluble polyolefin polymer on the chemically amplified resist film and an aromatic amine, aliphatic amine, or alkylamine-based basic compound;
Next, a step of performing a second heat treatment after performing pattern exposure;
Next, a step of developing after peeling the resin coating material film;
A resist pattern forming method comprising:

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